Conventionally, electrical junction boxes to be mounted in automobiles and the like are configured to include a box body that has a peripheral wall formed in a frame shape and keeps electric parts such as a relay, a fuse, and an electric wire installed inside the peripheral wall, and lid bodies such as an upper cover and a lower cover with which opening portions on the upper and lower sides of the box body are covered. For example, electrical junction boxes are configured as disclosed in JP 2012-55108A (Patent Document 1).
In Patent Document 1, a double wall portion, in which an inner wall and an outer wall extending in a peripheral direction are arranged with a clearance therebetween, is provided at the opening end portion on the lower side of the peripheral wall of the box body to which the lower cover is to be attached. An insertion wall portion provided at the tip end portion of the peripheral wall of the lower cover is inserted between the inner wall and the outer wall in this double wall portion in a close contact manner, and thus the lower cover is attached to the lower opening portion of the box body. Accordingly, even when the electrical junction box mounted in a vehicle is splashed with water, a route through which the water infiltrates from the outside into the inside of the electrical junction box becomes complicated due to the double wall portion and the insertion wall portion overlapping each other, and therefore, the water is advantageously prevented from infiltrating into the inside of the electrical junction box through the portion where the box body and the lower cover are fitted to each other.
However, in such an electrical junction box having a conventional structure, the double wall portion and the insertion wall portion overlap each other in a close contact manner, and therefore, there are cases where water infiltrates into the inside of the electrical junction box by capillary action through minute clearances formed between the contact surfaces of the inner wall and outer wall in the double wall portion and the contact surfaces of the insertion wall portion. Accordingly, there is still room for improvement.